Information storage devices are used to retrieve and/or store data in computers and other consumer electronics devices. A magnetic hard disk drive is an example of an information storage device that includes one or more heads that can both read and write, but other information storage devices also include heads—sometimes including heads that cannot write. For convenience, all heads that can read are referred to as “read heads” herein, regardless of other devices and functions the read head may also perform (e.g. writing, flying height control, touch down detection, lapping control, etc).
In a modern magnetic hard disk drive device, each read head is a sub-component of a head gimbal assembly (HGA). The HGA typically also includes a suspension assembly that includes a mounting plate, a load beam, and a laminated flexure to carry the electrical signals to and from the read head. The read head is typically bonded to a tongue portion of the laminated flexure. The HGA, in turn, is a sub-component of a head stack assembly (HSA) that typically includes a plurality of HGAs, a rotary actuator, and a flex cable. The mounting plate of each suspension assembly is attached to an arm of the rotary actuator (e.g. by swaging), and each of the laminated flexures includes a flexure tail that is electrically connected to the HSA's flex cable (e.g. by solder reflow bonding or ultrasonic bonding).
Modern laminated flexures typically include electrically conductive copper traces that are isolated from a stainless steel support layer by a polyimide dielectric layer. So that the signals from/to the head can reach the flex cable on the actuator body, each HGA flexure includes a flexure tail that extends away from the head along the actuator arm and ultimately attaches to the flex cable adjacent the actuator body. That is, the flexure includes electrically conductive traces that are electrically connected to a plurality of electrically conductive bonding pads on the head (e.g. by gold ball bonding), and extend from adjacent the head to terminate at electrical connection points at the flexure tail.
The read head typically comprises a slider that includes an air bearing surface (ABS) that faces the magnetic disk surface, a trailing face, and a back face that is opposite the ABS and that faces away from the ABS. A read/write transducer and a plurality of head bond pads are typically disposed on the trailing face of the slider. The read/write transducer typically comprises a magneto-resistive read element (e.g. so-called giant magneto-resistive read element, or a tunneling magneto-resistive read element), and an inductive write structure comprising a flat coil deposited by photolithography, and a yoke structure having pole tips that face a disk media. Conventionally, the back face of the slider is typically permanently bonded to the tongue portion of the fragile laminated flexure by an adhesive, in a position such that the plurality of head bond pads are aligned with corresponding bond pads on the laminated flexure.
The load beam of the HGA suspension assembly serves to preload the read head against the surface of the spinning disk, by a preload force conventionally known as the “gram load.” Such preload is functionally important to the development of the air bearing, since the pressure of the air bearing (when integrated across the air bearing surface) sums to be in equilibrium with the preload. Structurally, the preload is transferred from the load beam to the read head through a dimple contact interface between the load beam and the flexure tongue. For example, the dimple may protrude from the load beam and contact a flat surface of the flexure tongue, or else a dimple may protrude from the flexure tongue and contact the load beam.
The dimple contact is conventionally a stainless-steel-contacting-stainless-steel interface, which can become degraded by fretting wear over time. Specifically, fretting wear and corrosion may occur from prolonged relative pivoting motion at the dimple contact location, which may further cause undesirable stick and slip and corrosion at that interface, which also may create undesirable iron oxide particulate contamination within the disk drive. Hence, there is a need in the art for improved HGA suspension assembly structures and materials that may reduce wear or corrosion at the dimple contact location.